Anchorage control during tooth leveling and aligning

Introduction and definitions 94

Short-term versus long-term objectives 94 Principles of anchorage control 94 Treatment sequence to show leveling and aligning 95

Recognizing the anchorage needs of a case 96

Class II/1 example 96

("lass III example 97

Bimaxillary protrusion example 97

Bimaxillary retrusion - a Class 11/2 example 97

Mistakes in tooth leveling and aligning in the early years 98

Reduced anchorage needs during tooth leveling and aligning 99

Bracket design 99

Archwire forces 99

Avoidance of elastic chain 99

Antero-posterior anchorage support during tooth leveling and aligning 100

Lacebacks for A/P canine control 100 Bendbacks for A/P incisor control 102 A/P anchorage control of lower molars - the lingual arch 104

A/P anchorage control of lower molars - Class 111 elastics and headgear 104 A/P anchorage support and control for upper molars - the use of headgrear 105

A/P anchorage support and control for upper molars - the palatal bar 106

Vertical anchorage control during tooth leveling and aligning 106

Incisor vertical control 106

Canine vertical control 107

Molar vertical control in high-angle cases 107

Anchorage control in the lateral (coronal) plane 108

Inter-canine width 108

Molar crossbites 108

Exceptions to full bracket placement 109

Cases with unerupted teeth, or teeth significantly out of the arch form 109

Some high-angle deep-bite cases 109

Re-leveling procedures 109

Wire sequencing during tooth leveling and aligning 110

I listorical background I 10

Recommended sequencing 110

Heat-activated nickel-titanium or stainless steel? Ill

Clinical procedures in leveling and aligning -improving patient comfort and acceptance 112

Case LB Non-extraction average angle case 114

Case JN First premolar extraction case 120

INTRODUCTION AND DEFINITIONS

Principles of anchorage control n i O

Tooth leveling and aligning is normally the first orthodontic objective during the initial stage of treatment. It may be defined as:

The tooth movements needed to achieve passive engagement of a steel rectangular wire of .019/. 025 dimension and of suitable arch form, into a correctly placed preadjusted .022 bracket system.

Successful tooth alignment depends on recognizing that unwanted tooth movements can occur early in treatment, mainly owing to the tip built in to the preadjusted brackets. These unwanted tooth movements need to be controlled, or the underlying malocclusion will worsen during tooth alignment. This will increase the time and effort needed to complete the case, later in treatment.

During leveling and aligning, therefore, all tooth movements should be carried out with the final treatment goal in mind, and anchorage control measures should be used to restrict unwanted tooth movements. In this text, the term 'anchorage control during tooth leveling and aligning' will have the following meaning:

The maneuvers used to restrict undesirable changes during the opening phase of treatment, so that leveling and aligning are achieved without key features of the malocclusion becoming worse.

There are two main aspects to anchorage control:

1. Reduction of anchorage needs during leveling and aligning. There is a need to minimize the factors which threaten anchorage and which produce unwanted tooth movements. This reduces the demands on anchorage.

2. Anchorage support during tooth leveling and aligning. Where necessary, (here is a need to use anchorage support, such as palatal or lingual bars, to help to control certain teeth, or groups of teeth.

Anchorage control needs will differ from case to case. Measures to support anchorage control will not be needed in both arches, in every case. In some cases, for example in some Class 1 and Class 11/2 cases, no special measures will be required, and tooth alignment can proceed without regard to anchorage control. However, most cases do require proper anchorage control, and it is important to identify the needs for each individual case.

Short-term versus long-term objectives

It is helpful to consider leveling and aligning against a background of short-term and long-term objectives:

• The short-term objectives, in the opening months of treatment, will be to achieve proper leveling and aligning into passive rectangular steel wires.

• The long-term term objectives, to be reached by the end of treatment, will be to achieve an ideal dentition, showing the six keys to normal occlusion, and with the dentition properly positioned in the facial profile.

Experience has repeatedly shown that attempts to rush the short-term objectives, by taking short cuts and using heavy forces, cause unwanted changes to take place. These make achievement of the long-term objectives more time consuming and difficult.

Fig. 5.1 D After 4 months of treatment, it was possible to place upper and lower rectangular .019/.025 HANT wires. These very effective wires were used for several months, changing elastomeric modules and re-tying as necessary.

Treatment sequence to show leveling and aligning

Fig. 5.1A In this very crowded Class I case, the first premolars had previously been extracted. The upper right lateral incisor was in crossbite, and there was 2 mm of displacement at terminal closure.

Fig. 5.1 C Two months later. The upper right lateral incisor bracket was not inverted because the root position of this tooth was good, and special torque control was not required. A multistrand wire was used to continue tooth leveling and aligning in the upper, with a .014 round steel wire in the lower.

Fig. 5.1B Initial alignment was commenced with a .015 multistrand upper archwire and a .016 HANT lower archwire. A band with an eyelet was placed on the upper right lateral incisor. This was loosely tied.

Fig. 5.1 D After 4 months of treatment, it was possible to place upper and lower rectangular .019/.025 HANT wires. These very effective wires were used for several months, changing elastomeric modules and re-tying as necessary.

Accelerated Orthodontic Treatment

Fig. 5.1E Here the case is seen at completion of tooth leveling Fig. 5.1F The case after settling and appliance removal. Good and aligning. Steel rectangular wires, .019/ 025 in dimension tooth fit was assisted by the large size of the upper lateral and of ovoid arch form, are passively engaged in a correctly incisors, placed preadjusted .022 bracket system.

cd m

RECOGNIZING THE ANCHORAGE NEEDS OF A CASE

At the diagnosis and treatment planning stage for each case, a goal will be set for incisor position in the facial complex at the end of treatment. The determination of this 'planned incisor position' or PIP is explained on pages 166 to 169. The planned molar and canine changes will have been determined using the dental VTO.1

The anchorage control needs of a case, early in treatment, can be decided by comparing the starling position of upper and lower incisors with PIP at the end of treatment. During tooth leveling and aligning, the anchorage control should be managed to ensure that the upper and lower incisors either show no change, or they should move favorably relative to PIP. Ideally, incisor movement should be favorable, relative to PIP, throughout leveling and aligning, thereby reducing the amount of tooth movement needed later in the treatment.

Most of the concern will be with A/P changes, but torque control and vertical issues need to be considered and properly managed, where appropriate.

Anchorage needs for the molars and canines can be predicted from the dental VTO. These teeth should show no change, or preferably favorable change, relative to the VTO requirements.

In the following examples, the incisor starting position is shown in black, with the PIP in green, and comments are offered concerning the likely needs of the case. Every orthodontic case will be different, and the anchorage control needs will be determined by the position of the incisors relative to PIP, and not by the Angle's classification of the molars.

Class 11/1 example

At the start of treatment, the upper incisors are normally in front of PIP, and full A/P anchorage control will be required to restrict mesial movement and an increase in overjet. As discussed later in this chapter, upper arch anchorage control will involve lacebacks and bendbacks, and may require support from a palatal bar, a headgear, or Class II elastics.

Lower incisors will normally be on or behind PIP. Anchorage will need to be managed to prevent undue proclination during alignment. As with most cases, care will be needed to avoid excessive archwire forces, to eliminate the risk of a 'roller coaster' effect and deepening of the overbite.

Class III example

In this example, the upper incisors are behind PIP at the start of treatment, although in other Class 111 cases they may be on PIP or even in front of it. Lacebacks and bendbacks will therefore be contraindicated in the upper arch in many Class III cases, to allow upper incisors to procline and show favorable torque changes towards PIP, and to allow upper arch development.

Anchorage control will only be needed if there is a risk of overproclination of the upper incisors, beyond the PIP.

Lower incisors will typically be in front of PIP in a Class III case. The lower arch will therefore normally require full anchorage control with bendbacks and lacebacks, possibly supported with a lingual arch and/or Class 111 elastics.

Bimaxillary protrusion example

Normally full anchorage control will be required in both arches for this type of case, because upper and lower incisors will be in front of PIP at the start of treatment.

Interestingly, the mesializing effect of bracket tip often does not come into play in these cases, because the crowns are tipped mesially at the start. Despite this, full anchorage control is normally appropriate in the early stages, to ensure optimal retraction of the anterior segments.

Bimaxillary Protrusion

Fig. 5.4 Bimaxillary protrusion

Bimaxillary retrusion - a Class 11/2 example

In these cases, it is often a treatment requirement to allow upper and lower incisors unrestricted mesial movement in response to the opening archwires. Therefore lacebacks and bendbacks may be dispensed with, so that anterior bracket tip can express itself.

The starting malocclusion often has canines which are tipped distally - an indication for very light opening archwire forces. Favorable anterior torque and vertical changes typically occur in these cases, early in treatment, and they are often not difficult to manage in anchorage terms.

Retraction Anterior Teeth

Fig. 5.6 The tip built into the anterior brackets of the preadjusted appliance system causes the crowns of the anterior teeth to incline forward during early leveling and aligning.

Roller Coaster Effect Orthodontics
Fig. 5.7 Fig. 5.8 Fig. 5.9

Fig. 5.7 to 5.9 Use of elastic force for canine retraction, and excess force generally, produces a tendency for deepening of the anterior bite. Also, there is a tendency to lateral open bite, the overall outcome being referred to as the 'roller coaster' effect. In treatments in the 1970s and 1980s, the effects of elastic forces applied to canines early in extraction treatment with light archwires in place were found to be: (a) tipping and rotation into extraction sites; (b) bite opening in the premolar regions; (c) bite deepening anteriorly.

MISTAKES IN TOOTH LEVELING AND ALIGNING IN THE EARLY YEARS

Hie tip built into the anterior brackets of the preadjusted appliance system caused considerable difficulties in the early years. The tip caused the crowns of the anterior teeth to incline forward during the initial phase of leveling and aligning (Fig. 5.6).

Early attempts were made to eliminate or minimize this effect by connecting anterior segments to posterior segments, usually with elastic forces. But this created a greater demand for anchorage control during this initial stage of treatment. Also, if the elastic forces were greater than the leveling force of the archwire, there was a tendency for anterior teeth to tip and rotate distally, increasing the curve of Spee and deepening the bite. This was particularly evident in first premolar extraction cases, and was referred to as the 'roller coaster' effect (Figs 5.7-5.9).

The 'roller coaster' effect is seldom seen in today's cases, owing to the reduced tip in the MBT™ bracket system, lighter archwire forces, and use of lacebacks for canine control instead of elastic chain.

Fig. 5.6 The tip built into the anterior brackets of the preadjusted appliance system causes the crowns of the anterior teeth to incline forward during early leveling and aligning.

REDUCED ANCHORAGE NEEDS DURING TOOTH LEVELING AND ALIGNING

Where possible, the anchorage needs of a case should be reduced. This will lessen the need for anchorage control and support measures such as palatal and lingual bars or headgears, and this in turn will simplify the treatment and may make fewer demands on patient cooperation. The measures described below have been found to reduce demands on anchorage and thereby improve treatment efficiency.

Bracket design

Bracket tip is the major factor in anchorage demands early in treatment. Any reduction in built-in tip is beneficial in reducing the anchorage needs of a case. The MBTim VersatileH-bracket system is based on the original research values for tip. A total of 10° less distal root tip in the upper anterior segment and 12° less distal root lip in the lower anterior segment is needed, compared with the original SWA (Fig. 5.10). This reduces the anchorage needs, lessens the tendency to bite deepening in the early stages, and puts less demand on patient cooperation.

Archwire forces

The use of very light archwire forces (p. 112) early in treatment will be more comfortable for the patient, and will put less demand on anchorage. When unsure about which of two wires to use, it is normally preferable to use the lighter one. There is also a need to avoid changing wires too frequently.

Avoidance of elastic chain

As previously discussed (p. 98), many problems in the past emanated from the use of elastic retraction mechanics, especially in first premolar extraction cases. These should be avoided.

SWA tip
MBT" tip

Fig. 5.10 The MBT™ bracket system has 10° less distal root tip in the upper anterior segment and 12° less distal root tip in the lower anterior segment compared with SWA. This is beneficial in reducing anchorage demands early in treatment.

Chain Tooth Extraction

w ANTERO-POSTERIOR ANCHORAGE

* SUPPORT DURING TOOTH LEVELING AND

z ALIGNING

> Lacebacks for A/P canine control o n Lacebacks2 are .010 or .009 ligature wires which extend from the most distally banded molar to the canine bracket

H (I'igs 5.11 & 5.12). They restrict canine crowns from tipping

O forward during leveling and aligning. They are mainly used in premolar extraction cases, but they may also be required in c some non-extraction cases where there is a local threat to

=; anchorage. For example, if the root of a canine is mesially

O placed (Fig. 6.21, p. 140), this will effectively increase the tip q in the canine bracket at the start of treatment, and hence

O increase the anchorage needs of that tooth. X Lacebacks are passive devices, and should not be m overtightened to an extent that tissue blanching occurs. They Fig. 5.11 .010 or .009 ligature wires are used for canine m are placed before the archwire. At monthly adjustment visits, lacebacks, which are used mainly in premolar extraction cases.

^ the lacebacks are normally loose, and require 1-2 mm of

CD tightening. >

Fig. 5.12 Lacebacks have been an integral part of the authors' treatment philosophy for many years. This first premolar extraction case, treated in the 1980s with original SWA, shows upper and lower lacebacks in place. Lacebacks may be tied round the molar attachment or from the molar hook. If tied round the molar attachment, it is often necessary to use an explorer to prevent the laceback blocking the distal aspect of the molar tube.

Robinson3 investigated 57 premolar extraction cases, approximately half of which were treated with lacebacks and half without. His findings are summarized below (Fig. 5.13).

T he initial purpose of lacebacks was to prevent canines from tipping forward, but it was observed that, where necessary, these ligature wires were an effective method of distalizing the canines without causing unwanted tipping.

1.53mm

1.4mm

1.53mm

No laceback

No laceback

1.4mm

The most probable mechanism of this movement involves the initial slight tipping of the canine against the alveolar crest at the gingival aspect of the canines, followed by a period of 'rebound' owing to the leveling effect of the archwire, during which the roots of the canines are allowed to move distally (Fig. 5.14).

1.76mm

1.76mm

Laceback

Laceback

Fig. 5.13 The work of Robinson confirms that lower canine lacebacks have a beneficial effect in controlling proclination of lower incisors. Without lacebacks, on average the lower incisor moved forwards 1.4 mm. In contrast, with lacebacks in place, the lower incisors moved 1.0 mm distally.

Lacebacks are normally continued throughout the leveling and aligning archwire sequence, up to and including the rectangular I I ANT stage. Thereafter, in the rectangular steel wire stage, A/P control is continued with passive tiebacks (Fig. 9.17, p. 255).

During leveling and aligning, it is preferable to maintain the anterior six or eight teeth as a group, except in some midline problems, where canine retraction is called for (Fig. 5.15), and in some cases where it is necessary to maintain a Class I canine relationship (Case JN, p. 122). Accordingly, in most cases lacebacks are discontinued if a space occurs between the canine crown and the adjacent lateral incisor.

Lacebacks and bendbacks are the primary method of supporting anterior anchorage during leveling and aligning. Lacebacks minimize forward tipping of the canine crowns and can effectively retract them when indicated. Bendbacks are used to minimize forward tipping of the incisors, as discussed below.

Fig. 5.14 The probable action of the lacebacks on the canine during tooth leveling and aligning involves initial slight tipping followed by a period of rebound.

Fig. 5.15 In most treatments, it is preferable not to retract the canine away from the lateral incisor. However, in cases with small lateral incisors, midline discrepancies, or a need to maintain a Class I canine relationship, it may be appropriate to retract the canine away from the lateral incisor.

Fig. 5.15 In most treatments, it is preferable not to retract the canine away from the lateral incisor. However, in cases with small lateral incisors, midline discrepancies, or a need to maintain a Class I canine relationship, it may be appropriate to retract the canine away from the lateral incisor.

Incisor Relationship

Fig. 5.16A Bendbacks are an important method of anchorage support and can minimize forward tipping of incisors.

Bendbacks for A/P incisor control

These are used as an important method of anchorage support, often in combination with lacebacks. If the archwire is bent back immediately behind the tube on the most distally banded molar, this serves to minimize forward tipping of incisors (Pig. 5.16 A-C).

If the opening wire is .015 multistrand, it may be turned into a small circle distal to the molar tube (Fig. 5.17).

Fig. 5.16A Bendbacks are an important method of anchorage support and can minimize forward tipping of incisors.

Fig. 5.16C The softened end of the archwire can easily be turned in to form a bendback. The softening facilitates removal of the archwire at the subsequent adjustment visit.

Fig. 5.16B Steel and HANT wires should have the terminal 3 mm flamed and quenched before placement.

mmaam

Distal Finger Control Circles

Fig. 5.17 Multistrand wires may be carefully turned into a small circle distal to the molar tube to create a bendback.

Fig. 5.19 It is helpful to flame the end of all archwires, except steel rectangular and multistrand wires, and then quench them in cold water before placement. This allows accurate bendbacks.

Fig. 5.17 Multistrand wires may be carefully turned into a small circle distal to the molar tube to create a bendback.

T he ends of the .016 IIANT wires and round steel wires need to be flamed and quenched in cold water before placement, to allow accurate bendbacks (Figs 5.18 & 5.19). The rectangular HANT wires may be thinned at their terminal 3 mm and then flamed and quenched, to avoid de-bonding bonded molar tubes when creating bendbacks (Fig. 5.20) and to facilitate removal of the archwire for adjustment. A green stone is used for the thinning.

Like lacebacks, bendbacks are normally continued throughout the leveling and aligning archwire sequence, up to and including the rectangular I IANT stage, for any case which requires A/P control of incisors. Later, in the rectangular steel wire stage, the A/P control is continued with passive tiebacks (Fig. 9.17, p. 255, and Fig. 7.59, p. 186).

In cases where it is necessary to increase arch length during leveling and aligning (p. 40), and where A/P incisor control is not required, bendbacks should be placed 1 or 2 mm distal to molar tubes (F'ig. 7.16C, p. 171).

Fig. 5.18 Bendbacks are possible when using .016 HANT wires, providing the terminal 3 mm is flamed and quenched in cold water before placement of the archwire.

Fig. 5.19 It is helpful to flame the end of all archwires, except steel rectangular and multistrand wires, and then quench them in cold water before placement. This allows accurate bendbacks.

Fig. 5.20 Rectangular HANT wires may be thinned at their terminal 3 mm to allow creation of bendbacks after flaming and quenching.

H 73

cd cd

A/P anchorage control of lower molars -the lingual arch

Soldered lingual arches may be used in the late mixed dentition in cases with mild lower arch crowding. The lower first molars will normally drift mesially into the leeway space from the shedding of the lower primary second molars (Figs 5.21 & 5.22). This can be restricted by the timely placement of a lingual arch, and the space used to assist lower anterior alignment during tooth leveling and aligning.

Lingual arches should also be considered for maximum anchorage premolar extraction cases. This will include many bimaxillary proclination cases and also cases with severe lower anterior crowding. In both these types of problem, it is necessary to consider using a lingual arch throughout the early stages of leveling and aligning. This will restrict the mesial movement of lower molars, and in the bimaxillary proclination cases, it will ensure that most of the premolar extraction space is available at the end of leveling and aligning, to provide for retraction of the anterior segment. In the severely crowded cases, the lingual arch will ensure that most of the premolar extraction space is used to relieve anterior crowding (Case IN, p. 120).

A/P anchorage control of lower molars -Class III elastics and headgear

In cases with severe lower anterior crowding, where more anchorage support is needed than can be provided by a lingual arch alone, Class III elastics can be worn to Kobayashi tie wires in the lower canine region, at the same time as a headgear (Fig. 5.23). The authors prefer to delay Class III elastics until the .016 round wire stage, to prevent extrusion of the incisors. Fortunately, few cases require this amount of lower arch anchorage support.

Fig. 5.21 Lower lingual arches may be used to prevent first molars drifting mesially into the available leeway space after shedding of the lower primary second molars. This averages 2.5 mm.

Leeway Space
Fig. 5.22 Soldered lingual arches are helpful in maximum anchorage premolar extraction cases during tooth leveling and aligning. They normally need to be removed prior to space closure. They are also useful in protecting leeway space, as shown in this non-extraction case.
Combination Headgear
Fig. 5.23 Class III elastics can be worn in combination with a headgear for maximum anchorage support in the lower anterior segment.

A/P anchorage support and control for upper molars - the use of headgear

In certain cases, it may be necessary for the upper posterior segments to be limited in their mesial movement, maintained in their positions, or even distalized, to allow the anterior segments to be properly positioned in the face. I'osterior anchorage control requirements are normally greater in the upper arch than in the lower arch owing to five main factors:

1. The upper molars move mesially more easily than the lower molars.

2. The upper anterior segment has larger teeth than the lower anterior segment.

3. The upper anterior brackets have more tip built into (hem than the lower anterior brackets.

"Occlusal plane

Cervical

"Occlusal plane

Cervical

4. The upper incisors require more torque control and bodily movement than the lower incisors, which only require distal tipping or uprighting.

5. In many practices in America and Europe, a typical caseload has more Class II type of malocclusions than Class III type.

Because of these factors, extra-oral force is normally the most effective method of posterior anchorage control in the upper arch, provided sufficient patient cooperation is available. The three primary types of facebow headgear and their force directions are shown (Fig. 5.24).

The authors favor a combination headgear (occipital pull and cervical pull) in most cases. The force levels used for the combination headgear are 150-250gm for (lie occipital pull and 100-150gm for the cervical pull. These force values allow for slightly stronger pull on the occipital component of the headgear, keeping forces directed slightly above the occlusal plane and minimizing the tendency for vertical extrusion of the upper posterior teeth, while simultaneously allowing effective distalization of the molar.

The length of the outer bow of the headgear is important to avoid unwanted molar tipping. Ii should end adjacent to the upper first molar (lig. 5.25). An extended outer bow or an outer bow bent downward provides a greater tendency for distal tipping of the crown of the first molar. A shorter outer bow, or tipping up of the outer bow, causes a greater tendency for the roots to be distalized ahead of die crowns, as shown in the illustration. In high-angle cases where little distalization of the molar is required, an occipital headgear alone can be used. In veiy low-angle cases, where musculature is strong enough to minimize vertical extrusion of the posterior teeth, a cervical headgear alone can be considered.

Fig. 5.25 This diagram shows the theoretical effect of variations in the length of the outer arm of the headgear bow.
Mechanics For Palatal Canine

Fig. 5.26 Soldered palatal bars are helpful in restricting mesial movement of upper molars during tooth leveling and aligning.

Fig. 5.27 The tip which is built into the anterior brackets of the preadjusted appliance system gives a tendency to temporary increases in overbite early in treatment. If the canines are distally tipped in the starting malocclusion, then the bite-deepening effect is greater.

A/P anchorage support and control for upper molars - the palatal bar

A second method of anchorage support in the upper posterior segment is the palatal bar. This is normally placed when the upper molars have been properly rotated and are situated in a Class I relationship to the lower molars.

The palatal bar can be constructed of heavy .045 or .05 I inch (1.1 or 1.3 mm) round wire extending from molar to molar with a loop placed in the middle of the palate and the wire about 2 mm from the roof of the palate (Fig. 5.26 and 5.29). It is soldered to the molar bands.

VERTICAL ANCHORAGE CONTROL DURING TOOTH LEVELING AND ALIGNING

Vertical control of the incisors

As previously discussed, anterior control is needed to restrict the tendency to temporary increases in overbite (Fig. 5.27), especially in deep-bite cases. The effect of bracket tip is more extreme in the upper arch, and care is needed if the canines are distally tipped in the starting malocclusion. In such cases, as the archwire passes through the canine bracket slot it will lay incisally to the incisor bracket slots. If the wire is fully engaged into the incisors, it will tend to cause extrusion of these teeth, which is undesirable in most cases.

This effect can be avoided either by not bracketing the incisors at the start of treatment, or by not tying the archwire into the incisor bracket slots, but allowing it to lay incisally to the brackets until the canine roots have been uprighted and moved distally, under the control of the lacebacks. The incisors can then be engaged without causing unwanted extrusion.

Fig. 5.26 Soldered palatal bars are helpful in restricting mesial movement of upper molars during tooth leveling and aligning.

Vertical control of canines

It is important to avoid early archwire engagement of high labial canines (Case JN, p. 121), so that unwanted vertical movement of lateral incisors and premolars does not occur (Fig. 5.28).

Lateral Incisor Bracket
Fig. 5.28 High labial canines may be loosely tied to the .015 multistrand or .016 HANT wire in the early stages of treatment. If the starting archwire is fully engaged in the canine bracket slot, it can produce unwanted tooth movements in the adjacent lateral incisor and premolar regions.

Vertical control of molars in high-angle cases

When treating high-angle cases, the following methods of vertical molar control should be considered:

• Upper second molars are generally not initially banded or bracketed, to minimize extrusion of these teeth. If they require banding, an archwire step can be placed behind the first molar to avoid extrusion.

• If the upper first molars require expansion, an attempt is made to achieve bodily movement rather than tipping, to avoid extrusion of the palatal cusps. T his is best accomplished with a fixed expander, sometimes combined with a high-pull headgear.

Headgear Cervical
Fig. 5.29 If the upper palatal bar is placed 2 mm away from the palate, tongue forces can assist in vertical control of the molars.

If palatal bars are used, they are designed to lie away from the palate by approximately 2 mm so that the tongue can exert a vertical intrusive effect (Fig. 5.29).

When headgears are used in high-angle cases, either a combination pull or a high-pull headgear is used. The cervical pull headgear is avoided.

In some cases, an upper or lower posterior biteplate in the molar region is helpful to minimize extrusion of molars.

Molars Lying Laterally

Fig. 5.30 Upper molar expansion should be carried out by bodily movement rather than tipping. Minimal molar crossbites can be corrected using rectangular steel wires which are slightly expanded from the normal form and which carry buccal root torque.

w ANCHORAGE CONTROL IN THE LATERAL * (CORONAL) PLANE

x In most cases, no special care is needed to maintain lateral

O anchorage control. However, attention needs to be paid to

> inter-canine width in all treatments, and molar crossbites are

m important in certain treatments, n O z g Inter-canine width r~

D Upper and lower inter-canine width should be kept as close as

§ possible to starting dimensions for stability, and care should

2 be taken to ensure that crowding is not relieved by

H uncontrolled expansion of the upper and lower arches.

^ Molar crossbites rn

¡H Care is needed to avoid arbitrary correction of molar

2» crossbites by tipping movements. This allows extrusion of palatal cusps and unwanted opening of the mandibular plane 2 angle in treatment of high-angle, and even routine, Class Il/l problems. Whenever possible, molar crossbites should be ^ corrected by bodily movement.

^ An assessment of maxillary bone can be made, and if it is

=; too narrow, early rapid expansion should be considered as a

CD separate procedure prior to leveling and aligning. If adequate maxillary bone exists, a fixed quadhelix expander can be effectively used. Minimal molar crossbites can usually be corrected in the final stage of leveling and aligning using rectangular wires which are slightly expanded from the normal form (Fig. 5.30).

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